1. Field of the Invention
The present invention relates to an observation apparatus for the behavioral observation of experimental animals, such as mice, rats or hamsters, employing optical sensors to measure the actions of the experimental animal.
2. Description of the Prior Art
Novel medical supplies and foodstuffs are under a legal obligation to undergo safety tests including long-term animal experiments. The behavioral observation of an experimental animal is one of the modes of animal experiments. Since the continuous visual observation of the actions of an experimental animal is impossible, the behavior of the experimental animal is monitored by optical sensors to determine the positions of the experimental animal, the data obtained by the optical sensors is analyzed logically and the behavior is represented by numerical data. As shown in FIG. 5, a conventional apparatus for the behavioral observation of an experimental animal comprises a cage 1 having the shape of a rectangular solid, and optical sensors arranged along the X-axis and the Y-axis, which are perpendicular to each other, to measure only the two-dimensional positions, the width and length of an experimental animal, i.e., a mouse M.
Catching the experimental animal only within a plane, this conventional observation apparatus is unable to detect peculiar standing actions and delicate actions, such as the swing motions of the head within the width Ya of the body, of the experimental animal. Furthermore, being unable to detect the three-dimensional actions of the experimental animal and detecting the actions of the tail and the body inclusively, the conventional observation apparatus is unable to provide detailed measured data.
Although an optical sensor may be arranged for three dimensional detection, increase in the number of the optical sensor inevitably increases the cost of the observation apparatus. Furthermore, if the space defined by the side walls of the cage is not extraordinarily large, the advancement of the experimental animal is limited by the side walls of the cage having the shape of a rectangular solid and hence the continuous movement of the experimental animal is restricted. Consequently, the arbitrary or spontaneous actions of the experimental animal are restricted and the experimental animal is obliged to act under physical restrictions, which deteriorates the accuracy of measured data.